β-Ketophosphonic acid according to general formula I:in which A=an aliphatic C1-C18 radical which can be interrupted by —O—, —S—, —CO—O— or —O—CO—C—； n=1, 2, 3 or 4； m=1 or 2； X=absent or a C1-C10 radical which can be interrupted by —O—, —S—, —CO—C—, —O—CO—NH— or —CO—NR1—, wherein R1 is H or C1-C7-alkyl； and PG=a group which can undergo free radical polymerization. The β-ketophosphonic acids are suitable in particular for the preparation of dental materials.
